From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F1630C4361B for ; Thu, 10 Dec 2020 20:22:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B819523D57 for ; Thu, 10 Dec 2020 20:22:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390095AbgLJUWj (ORCPT ); Thu, 10 Dec 2020 15:22:39 -0500 Received: from mx2.suse.de ([195.135.220.15]:37692 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728036AbgLJUWi (ORCPT ); Thu, 10 Dec 2020 15:22:38 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id ACAE9AC6A; Thu, 10 Dec 2020 20:21:57 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id DE15EDA842; Thu, 10 Dec 2020 21:20:20 +0100 (CET) Date: Thu, 10 Dec 2020 21:20:20 +0100 From: David Sterba To: Johannes Thumshirn Cc: Sidong Yang , "linux-btrfs@vger.kernel.org" Subject: Re: [PATCH] btrfs-progs: scrub: warn if scrub started on a device has mq-deadline Message-ID: <20201210202020.GH6430@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Johannes Thumshirn , Sidong Yang , "linux-btrfs@vger.kernel.org" References: <20201205184929.22412-1-realwakka@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Mon, Dec 07, 2020 at 07:23:03AM +0000, Johannes Thumshirn wrote: > On 05/12/2020 19:51, Sidong Yang wrote: > > Warn if scurb stared on a device that has mq-deadline as io-scheduler > > and point documentation. mq-deadline doesn't work with ionice value and > > it results performance loss. This warning helps users figure out the > > situation. This patch implements the function that gets io-scheduler > > from sysfs and check when scrub stars with the function. > > From a quick grep it seems to me that only bfq is supporting ioprio settings. Yeah it's only BFQ. > Also there's some features like write ordering guarantees that currently > only mq-deadline provides. > > This warning will trigger a lot once the zoned patchset for btrfs is merged, > as for example SMR drives need this ordering guarantees and therefore select > mq-deadline (via the ELEVATOR_F_ZBD_SEQ_WRITE elevator feature). This won't affect the default case and for zoned fs we can't simply use BFQ and thus the ionice interface. Which should be IMHO acceptable.